Consistent with quantitative MRI data, ventricular and sulcal atrophy was significantly greater in older than younger participants, and atrophy was greater in older men than women. Older participants showed more extensive white matter abnormalities than younger participants, and this age difference was similar for men and women. PET imaging studies of regional cerebral blood flow showed that both the verbal and figural recognition memory tasks activate right prefrontal regions, bilateral visua association areas, and left cerebellar regions. Estrogen replacement therapy (ERT) was examined as a risk for Alzheimer~s disease. Approximately 48% of the women in the cohort had used ERT; 34 incident cases of AD were diagnosed during follow-up, including 9 estrogen users. After adjusting for education, the relative risk for AD in ERT users compared to non-users was 0.46 (95% CI=0.209-0.997), indicating a reduced risk of AD for women who had reported the use of estrogen